northgawx

Good morning/afternoon/evening (depending on when you are reading this) everyone.

The stage is being set for what is looking to be by far the best potential for a major winter storm we have seen in quite some time across north GA. The Euro and it’s ensemble mean have been extremely consistent with this threat, and as of tonight the UKMET (guess where it’s from) and Canadian, as well as to some extent the GFS, have come on board with a major winter threat next Monday-Wednesday. It will come in two stages so let’s take a look at each one individually.

MONDAY-OVERRUNNING EVENT

The first of two stages will come in the form of a potential overrunning event. What is overrunning? Basically what we saw a couple weeks ago where moisture rides up over a cold airmass that provides enough lift to produce light/moderate snow. The global models missed the last threat for the most part, though the GFS handled it fairly well once the event got close. You can see a classic “finger” of moisture being shown across the entire 0z model suite.

GFS valid mid-morning Tuesday. Notice the overrunning precip occurring over the cold air in north AL/GA. Surface temps are below freezing at this point for areas north of Gainesville->Dawsonville. Verbatim this run produces 1-3″ of snow but those amounts would likely be higher in the event this plays out. Nearly every system this winter has over-produced on precip and I suspect this would be no different.

And on the CMC:

UKMET at 72 hours (the furthest precip maps I have). You can see hte moisture streaming out of the gulf across MS/AL and points north/west.

The Euro shows a similar set-up with an initial wave of overrunning precip producing several inches of snow for parts of the area.  Immediately behind this first wave of precip comes the big dog Tuesday night and Wednesday.

THE BIG DOG

I’m going to start this by dismissing the GFS. Why? It has a bias of stringing out energy and we have seen it do it many times this winter, only to come around once we get closer. I suspect the traditional GooFuS 3-5 day out shenanigans again. Not to mention it has no support from the Euro/CMC/UKMET at this point. It could be seeing something the others are not, but the Euro Ensembles (EPS) back the Euro up. So now that tha tis out of the way….

The Euro/CMC/UKMET/EPS all show some form of major winter storm impacting the area from late Tuesday through the day Wednesday. Exactly what type of winter storm remains to be seen, though it is looking increasingly likely the second wave will come through as possibly a major ice storm for a good portion of GA/SC/NC, and possibly as far south as the Macon area, though the southern extent is quite difficult to ascertain at this point.   Here’s the keys to watch as we head through the timeframe, however.

First off, the low pressure system: this seems to be the thing the GFS doesn’t like very much, as it string the energy out badly and is much, much slower than the rest of the modeling world. The Euro/CMC/UK all have a healthy gulf low pressure system moving in late Tuesday, spreading precip across the entire area by Tuesday night with surface temps for the most part below freezing from ATL north/eastward. I somewhat suspect they are overdoing surface temps a bit, especially with the snowcover from the earlier overrunning event, putting places further south/west in play for ice.   The other key will be the CAD (cold air damming/wedge) event ongoing. The E/C/U all keep the CAD event fairly strong (strong enough, anyways) for the duration of the event, keeping surface temps at or below freezing north/west of an Athens to Ellijay line (the classic wedge zones). Climatologically speaking this type set-up generally yields a good wedge event with snow in the far northeastern corner and freezing rain elsewhere. Which brings me to my final point for tonight: snow or freezing rain?

That is the question. And we might as well throw sleet in there as the CMC gives us a good sleet storm to kick things off. Ultimately at some point we would see a changeover to freezing rain for pretty much everyone, the question is just how quickly does that occur. Current trends suggest a prolonged freezing rain event from Tuesday night through the day Wednesday finally moving out Wednesday evening. THE POTENTIAL EXISTS FOR A MAJOR ICE STORM WITH THIS SYSTEM. It has been quite some time (2005) since our area saw a major ice storm (more than .25″ of ice) and the worst case scenario for this system would be much worse than that one.

All this said, my confidence is much higher than normal for a system still 4 days away, but this is a winter forecast in the south and it is well known how hard they are to forecast. The biggest confidence booster for me personally is that of the 52 Euro ensemble members, only 5 or six don’t show a major winter storm for the area, and now that the Canadian/UK have joined the boat it’s hard to argue against them. I’ll be updating more as we get closer (the overrunning event is really only 3 days away since it begins Monday night) but for now just be advised of the potential for a major winter storm next week, with impacts beginning as early as Monday night.

~TW